Lime per Acre

Hello, looking for some advice on a good lime per acre rate. I have some hay fields I want to top coat lime. The rates the cooperative and the dealer gave me are different. The fields are Timothy, brome, Orchard grass mix. My PH was 5.6 on one. And 5.8 on the other. Any info would be appreciated. Thanks.

Your PH is on the pretty low side. My guess would be, depending on your soil type (clay, sand, loam, etc.), around 4 tons/acre. However, top dressing that much in one pass probably won't work too well because lime only migrates 1/8th to 1/4 inches into the soil per year.

My suggestion would be to apply about 2 tons/acre this year, then 1 ton next year. Then wait one year (the third year) and test again for PH to see if you need to add 1-2 tons more.

While this increases the cost of spreading, the effectiveness of the lime will increase. If you were incorporating the lime by discing 8-12 deep, you could apply 4 tons at once and be OK.

Does discing kill a lot of the stand by cutting the crop, or does it actually invigorate, airerate the top layer and aid in growth?
Can you disc/lime pretty much any time over the winter as long as there's no frost? Or is there a typical season for discing (located in mid-atlantic)

Does discing kill a lot of the stand by cutting the crop, or does it actually invigorate, airerate the top layer and aid in growth?Can you disc/lime pretty much any time over the winter as long as there's no frost? Or is there a typical season for discing (located in mid-atlantic)

No, aggressive enough discing to incorporate lime will kill the stand. The soil needs to be rolled over enough times so that the lime is "stirred" into the soil--kinda like mixing a cake batter.

Discing to incorporate is usually done when preparing the ground for a new stand. I spread the lime and fertilizer first, then make 2-4 passes to spread the goodies into the top 8-10" evenly. At least two passes, but sometimes more are needed depending on the soil conditions (wet, dry, compacted, etc.) and type.

You might think of top-dressing as the plant trying to eat only the icing on a cake. But you want the plant roots go deep for moisture, so the nutrients are on top and the moisture is down deep. You'll get real good plant growth IF you have enough moisture, but once things dry out, you plants start dieing because they have only been feeding on the icing.

The attached graph shows that we don't always achieve the soil mixing that we intend by disking. The file shows that two attempts to disk incorporate limestone 6-inches deep (in a sandy loam soil with an initial pH at 5.2) immediately following application (pH tested at 7 months) and again at 7-months later (pH tested at 12 months) failed to change soil pH much deeper than 2 - 3 inches. At 12 months the field was moldboard plowed and disked again (pH tested several months later). Soil pH was now changed fairly uniformly down to the 6-inch depth. Because the limestone was now diluted into the 6-inch depth, pH at the soil surface was lower than what it was before plowing.

Soil pH for most forage crops need not be much above 6.0 - 6.2, except for alfalfa and possibly Tifton 85 bermudagrass where the desired pH for optimum plant growth needs to be pH 6.8 to 7.0. Even higher is okay but above pH 8.3 or so, problems with nutrient tie-up could occur for sensitive crops. At pH 5.6 to 5.8 in a sandy loam soil, one ton of effective calcium carbonate equivalence limestone (ECCE; a very fine pure calcium carbonate material) should raise soil pH to the 6.0 - 6.2 range. If the soil is a heavy clay, more limestone will be needed to change pH to this level.

If disking will kill your type of grass, by necessity the limestone needs to be left on the soil surface where it will be much slower to react because it is not in good contact with soil acidity. Someone with experience with your types of grasses would need to advise you about the possibility of very light disking and damage to the grass stand.

Those of us with stands of hybrid bermudagrass can disk incorporate limestone without killing the grass as long as disking is done at the time the grass begins to green up in spring and the soil is fairly moist. At this time, disking essentially resprigs the bermudagrass which puts out roots at nodes of rhizomes. A requirement for success at this time is that the freshly disked soil must be repacked with a heavy roller to seal in the moisture, and a good rain after disking also would help.

The max amount of our course limestone that I spread is 2 tons to the acre with a ph of 5.5 on up. My father always told me that if you spread more than 2 tons/per acre, you were wasting your money. Now I don't know the foundation of that statement, but I have always lived by that ( going on blind faith )and all of my fields stay in the 6.3 to 6.9 range with just a ton of lime added on some fields as needed. I was taking soil samples this fall and noticed that the ph had gone from 6.5 to 5.8 on one farm that suffered from the drought this summer. Upon talking to the lab technician, he informed me that he was seeing a lot of ph's falling off because of the drought, so he thought. He is suppose to follow up with me for more info. So if you were in a drought situation as I was on one farm, maybe you should take some soil samples this fall. Just a thought. Mike

I was taking soil samples this fall and noticed that the pH had gone from 6.5 to 5.8 on one farm that suffered from the drought this summer. Mike

Possibly why your soil pH went down:

Soil pH varies from spring to fall. Most testing labs measure soil pH in a soil:water suspension, usually 1:1 or 1:2 soil:distilled water. Salt, even a very slight amount, in soil lowers the soil:water pH. What causes this to occur? From spring to fall, the soil is being fertilized (adding salt) and as the hot summer proceeds toward fall, the soil is drying and the soil salt content is becoming more concentrated. Soil samples collected in fall will show the salt-effected pH reading and it will be as much as 0.5 to 1.0 pH unit lower than in samples collected in spring because during winter, increased rainfall and less fertilizer addition allow the soil salt concentration to be washed out of the soil (leached). This salt-effected pH is more pronounced in lower buffer capacity soils (soils that have a lower capacity to resist chemical change) such as loamy sand, sandy loam, etc. compared to higher clay content soils.

I believe that the salt-effected pH is closer to the true pH of a soil, but few testing labs are willing to change their pH testing procedure by adding a very slight amount of calcium chloride to the distilled water pH test. These labs are concerned that testing pH in a dilute salt will create confusion among producers who wonder why their soil pH is now reading lower.

You can avoid this situation by always collecting soil samples in fall so that the pH test reflects the salt-effected lower pH, similar to what occurred with Mike's sample. Or, if you prefer, always collect soil samples in spring, but don't switch from spring to fall sampling if you want to avoid the salt-effected pH and receive a higher pH reading than what may actually exist in the soil.

Lime recommendations should be made using buffer pH tests or from other tests that determine the actual acidity in soil and not simply from the normal soil:water pH.

Vhaby, I take soil samples both spring and fall for all of my fields. This particular field is the only one that is low so how could that be? I have sent off some more samples to recheck. We will see. As a side note, our drought was widespread over 3 of my farms so this does not make sense to my ole brain. Thanks, Mike